Engine system and cogeneration equipment equipped with the same

Abstract

To improve shaft output (improve thermal efficiency) by simple control while sufficiently reducing energy supply related to reforming of ammonia when ammonia and hydrogen obtained by reforming a part of the ammonia are used as fuel gas.SOLUTION: An engine system includes: a control device R for controlling an operation; a reformer RF for reforming a part of ammonia N to generate a reformed gas K containing a combustion-accelerating gas having a high combustion rate; and a temperature adjustment unit L4b for combusting the ammonia N and the reformed gas K generated by the reformer RF together with a combustion air A2 in a combustion chamber, and adjusting a temperature of the reformer RF using an exhaust gas E from the combustion chamber. The control device R performs ignition timing control for retarding an ignition timing when performing output increase control for increasing shaft output, and advancing the ignition timing when performing output reduction control for reducing shaft output.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an engine system including a control device for controlling operation and a reformer for reforming a portion of ammonia to produce a reformed gas containing hydrogen, and for burning ammonia and the reformed gas produced in the reformer as fuel together with combustion air in a combustion chamber, and to a cogeneration facility including the engine system. [Background technology]

[0002] Conventionally, various engine systems have been proposed as engine systems using ammonia as a main component. In view of the fact that ammonia is flame-retardant, an engine system is known in which part of the ammonia is reformed into hydrogen, which has high ignition properties, and the reformed hydrogen is used as fuel together with ammonia. As an example of such an engine system, as shown in Patent Document 1, there is known an engine system that includes a combustor that burns ammonia, a reformer that reforms the ammonia, and an engine that uses ammonia and hydrogen reformed by the reformer as fuel. In the engine system disclosed in Patent Document 1, the reforming reaction of ammonia is an endothermic reaction, so the reformer is heated by combustion gas obtained by burning ammonia in a combustor, and reforming in the reformer is carried out in such a manner that heat related to the reforming reaction in the reformer is supplied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-92809 Summary of the Invention [Problem to be solved by the invention]

[0004] In the engine system disclosed in Patent Document 1, it is necessary to provide a combustor in order to promote the reforming reaction in the reformer, and it is also necessary to supply ammonia as fuel for generating combustion gas in the combustor. Furthermore, in order to control the reforming reaction in the reformer, the combustion state of the combustor must be controlled separately from the control of the engine, which requires a relatively complicated configuration.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an engine system and a cogeneration facility equipped with the engine system, which can improve shaft output (improve thermal efficiency) through simple control while sufficiently reducing the energy supply related to the reforming of ammonia when ammonia and hydrogen obtained by reforming a part of the ammonia are used as fuel gas. [Means for solving the problem]

[0006] The engine system for achieving the above object comprises: a control device for controlling the operation; a reformer that reforms a portion of the ammonia to generate a reformed gas containing a combustion-promoting gas having a high combustion rate, An engine system in which ammonia and the reformed gas generated in the reformer are combusted as fuel together with combustion air in a combustion chamber, and the engine system has the following characteristic configuration: a temperature adjusting unit that adjusts the temperature of the reformer using exhaust gas from the combustion chamber; The control device performs ignition timing control to retard the ignition timing when performing output increase control to increase the shaft output, and to advance the ignition timing when performing output reduction control to reduce the shaft output.

[0007] According to the above characteristic configuration, firstly, since a temperature adjustment unit is provided that adjusts the temperature of the reformer using exhaust gas from the combustion chamber, the heat used in the ammonia reforming reaction, which is an endothermic reaction, can be provided by the exhaust gas from the combustion chamber. This eliminates the need to provide a combustor for the reforming reaction, and also eliminates the need to consume ammonia that is used only to promote the reforming reaction in the combustor, thereby reducing the energy supply related to reforming. In the engine system described above, ammonia is flame-retardant and there is a risk of misfires, etc., so when improving the shaft output, simply increasing the amount of ammonia fuel does not necessarily result in a stable increase in shaft output. Therefore, in the above-described characteristic configuration, the control device executes ignition timing control to retard the ignition timing when executing power increase control to increase the shaft output, and to advance the ignition timing when executing power reduction control to reduce the shaft output. In particular, by retarding the ignition timing in the combustion chamber (in particular, by retarding it to a timing later than top dead center), combustion in the combustion chamber is slowed, adjusting the balance between the engine's shaft output and thermal output (thermal output to exhaust gas) to increase the thermal output, and using the heat from the exhaust gas to heat the reformer to promote the reforming reaction and increase the amount of reformed gas produced in the reformer. Because the increased reformed gas contains combustion-promoting gases such as hydrogen, introducing the reformed gas into the combustion chamber improves combustibility in the combustion chamber and enables the engine's shaft output to be increased. Furthermore, according to this control, the engine shaft output is increased by increasing the amount of combustion-promoting gas introduced into the combustion chamber, so it is expected that the thermal efficiency will be improved compared to when control is performed in the direction of directly burning flame-retardant ammonia in the combustion chamber. As described above, when ammonia and hydrogen obtained by reforming a portion of it are used as fuel gas, an engine system can be realized that can improve shaft output (improve thermal efficiency) through simple control while suppressing the energy supply related to the reforming of ammonia.

[0008] Further characteristic configurations of the engine system include: The ignition timing control is performed by retarding the ignition timing within a range from a first retard limit to a second retard limit on the top dead center side when natural gas is used as the fuel gas.

[0009] Through careful study, the inventors have confirmed through simulations that by retarding the ignition timing in ignition timing control within a range from the first retard limit to a second retard limit on the side of top dead center when natural gas is used as the fuel gas, it is possible to effectively reduce ammonia misfire in the combustion chamber while also effectively improving the engine output.

[0010] Further characteristic configurations of the engine system include: a hydrogen concentration measuring unit for measuring the hydrogen concentration of the reformed gas; The control device is characterized in that, in the ignition timing control, the higher the hydrogen concentration of the reformed gas measured by the hydrogen concentration measuring unit, the more retardation limit setting control is performed to set the second retardation limit to the retard side.

[0011] According to the above characteristic configuration, in ignition timing control, the control device executes retardation limit setting control in which the second retardation limit is set to the retard side as the hydrogen concentration of the reformed gas measured by the hydrogen concentration measurement unit becomes higher. Therefore, in view of the effect that the high hydrogen concentration contained in the reformed gas and the high ignition ability of the hydrogen can suppress misfires in the combustion chamber, the retardation limit can be expanded, thereby expanding the operating range.

[0012] Further characteristic configurations of the engine system include: a hydrogen concentration measuring unit for measuring the hydrogen concentration of the reformed gas; The control device is characterized in that, in the ignition timing control, the lower the hydrogen concentration of the reformed gas measured by the hydrogen concentration measuring unit, the more it performs retard amount correction control to correct the ignition timing retard amount to a smaller value.

[0013] As has been explained so far, in the engine system according to the present invention, for example, when attempting to transiently increase the engine output (increase the shaft output), the ignition timing is retarded. However, when the fuel introduced into the combustion chamber is mainly ammonia, for example, there is a risk that the retardation of the ignition timing will increase the possibility of misfires occurring, since ammonia is flame-retardant. Furthermore, when the ignition timing is retarded to raise the temperature of the exhaust gas and thereby raise the temperature of the reformer, there is a slight time lag between the time the ignition timing is retarded and the time the reformer temperature rises. As described in the above characteristic configuration, in ignition timing control, the lower the hydrogen concentration of the reformed gas measured by the hydrogen concentration measurement unit, the more retardation amount correction control is executed to correct the ignition timing retard amount to a smaller amount. For example, when the control device is retarding the ignition timing to increase the shaft output by a predetermined increment, and the reformer has not yet been sufficiently heated by the exhaust gas and the hydrogen concentration of the reformed gas from the reformer is low, the retardation amount can be corrected to a smaller amount to prevent combustion from becoming unstable.

[0014] Further characteristic configurations of the engine system include: a temperature measurement unit for measuring a temperature-related value related to the temperature of the reformed gas; The control device is characterized in that, in the ignition timing control, the lower the temperature-related value of the reformed gas measured by the temperature measurement unit, the more it performs retard amount correction control to correct the ignition timing retard amount to a smaller value.

[0015] As has been explained so far, in the engine system according to the present invention, for example, when attempting to transiently increase the engine output (increase the shaft output), the ignition timing is retarded. However, when the fuel introduced into the combustion chamber is mainly ammonia, for example, there is a risk that the retardation of the ignition timing will increase the possibility of misfires occurring, since ammonia is flame-retardant. Furthermore, when the ignition timing is retarded to raise the temperature of the exhaust gas and thereby raise the temperature of the reformer, there is a slight time lag between the time the ignition timing is retarded and the time the reformer temperature rises. As described in the above characteristic configuration, in ignition timing control, the lower the temperature-related value of the reformed gas measured by the temperature measurement unit, the more retardation amount correction control is executed to correct the ignition timing retard amount to a smaller amount.For example, when the control device controls the ignition timing retard amount to a value corresponding to the target shaft output, and the reformer has not yet been sufficiently heated by the exhaust gas and the hydrogen concentration of the reformed gas from the reformer is low, the retardation amount can be corrected to a smaller amount to prevent combustion from becoming unstable.

[0016] Further characteristic configurations of the engine system include: The control device causes a mixture of the fuel and the combustion air to be stoichiometrically combusted in the combustion chamber, and The feature is that a three-way catalyst is provided in the exhaust passage through which exhaust gas from the combustion chamber flows.

[0017] When ammonia is burned, the exhaust gas contains nitrogen oxide components. However, in a configuration in which a three-way catalyst is provided in the exhaust passage through which exhaust gas from the combustion chamber flows, as in the above-described characteristic configuration, the control device causes a mixture of fuel and combustion air to be burned stoichiometrically in the combustion chamber, and the three-way catalyst can effectively remove the nitrogen oxide components contained in the exhaust gas discharged from the combustion chamber burning stoichiometrically.

[0018] According to a cogeneration facility equipped with the engine system described above, the effects and advantages of the engine system described above can be effectively achieved. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic configuration diagram of an engine system according to an embodiment. [Figure 2] FIG. 2 is a control flow diagram of the engine system according to the embodiment. [Figure 3] FIG. 10 is a schematic configuration diagram of an engine system according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] As shown in FIG. 1, an engine system 100 according to an embodiment of the present invention and a cogeneration facility 200 including the engine system 100 can improve shaft output (improve thermal efficiency) through simple control when ammonia N and hydrogen obtained by reforming a part of the ammonia N are used as fuel gas.

[0021] [Engine System] The engine system 100 includes a control device R that controls operation, and a reformer RF that reforms a portion of ammonia N to produce a reformed gas K containing a combustion-promoting gas (e.g., hydrogen) with a high combustion rate, and the ammonia N and the reformed gas K produced in the reformer RF are combusted as fuel together with combustion air A2 in a combustion chamber (not shown) of the engine body 40. The shaft output of the engine body 40 is used as a power source that rotates and drives a generator (not shown) or the like.

[0022] The engine system 100 includes a combustion air passage L2 that supplies combustion air A2 to the engine body 40, a reforming air passage L1 that supplies reforming air A1 to the reformer RF, a fuel passage L3 that conducts ammonia N as fuel to the reformer RF and the engine body 40, an exhaust gas passage L4 (an example of an exhaust path) that conducts exhaust gas E from the engine body 40, and a reformed gas passage L5 that conducts reformed gas K generated in the reformer RF to the combustion air passage L2 at the inlet of the engine body 40.

[0023] The reformer RF is an auto-thermal reformer that uses heat generated by burning vaporized ammonia N to reform the ammonia N, thereby generating reformed gas K containing hydrogen. The reformer RF has a reforming catalyst (not shown) disposed in its housing (not shown).

[0024] The reforming catalyst (not shown) has, for example, a honeycomb structure, and is a catalyst that burns vaporized ammonia N and decomposes the ammonia N into hydrogen. As the reforming catalyst, for example, a cobalt-based catalyst, a rhodium-based catalyst, a ruthenium-based catalyst, a palladium-based catalyst, or the like is used.

[0025] The fuel flow path L3 is composed of a first fuel flow path L3b having a reforming injector IJ1 as an electromagnetic fuel injection valve that injects ammonia N vaporized in a vaporizer 31 that vaporizes ammonia N stored in a cylinder (not shown) into the reformer RF, and a second fuel flow path L3a having an engine injector IJ2 as an electromagnetic fuel injection valve that injects the ammonia N vaporized in the vaporizer 31 into the combustion chamber of the engine body 40.

[0026] The reforming air passage L1 is equipped with a first air cleaner 11 that purifies the reforming air A1 and an electromagnetic reforming throttle valve 12 that controls the flow rate of the reforming air A1 supplied to the reformer RF, and the reforming air A1 flowing through the reforming air passage L1 and ammonia N injected from the reforming injector IJ1 are supplied to the reformer RF.

[0027] In the reformer RF, when the temperature of the internal reforming catalyst (not shown) is raised to the catalytic activation temperature by heating using a heater L4b (described later), the reforming catalyst causes an exothermic reaction according to the following formula 1, and the temperature of the reforming catalyst further rises due to the self-heat of the reforming catalyst.

[0028] NH3+3 / 4O2→1 / 2N2+3 / 2H2O... [Formula 1]

[0029] Furthermore, when the temperature of the reforming catalyst reaches the reaction temperature (described above), the ammonia N is reformed by the reforming catalyst. Specifically, as shown in the following formula 2, a decomposition reaction of ammonia N occurs (endothermic reaction), and reformed gas K containing hydrogen is produced.

[0030] NH3→3 / 2H2+1 / 2N2... [Formula 2]

[0031] The reformed gas flow path L5, through which the reformed gas K generated in the reformer RF flows, is equipped with a hydrogen sensor S1 (an example of a hydrogen concentration measuring unit) that measures the hydrogen concentration contained in the reformed gas K generated in the reformer RF, an intercooler 13 that cools the flowing reformed gas K by heat exchange with cooling water, and an electromagnetic flow control valve V1 that controls the flow rate of the flowing reformed gas K.

[0032] The combustion air passage L2 is equipped with a second air cleaner 21 that purifies the combustion air A2 and an electromagnetic main throttle valve 22 that controls the flow rate of the combustion air A2 supplied to the engine body 40. In addition, the combustion air passage L2 is provided with an inlet L5a for the reformed gas K from the reformed gas passage L5. Furthermore, ammonia N as fuel is injected from an engine injector IJ2 at a connecting portion of the combustion air passage L2 to a combustion chamber (not shown) of the engine body 40.

[0033] The exhaust gas flow path L4, through which the exhaust gas E from the engine body 40 flows, is provided with a heater L4b (an example of a temperature adjusting unit) as a flow path for the exhaust gas E that surrounds the reforming catalyst along the inner circumferential surface of the substantially cylindrical housing inside the housing of the reformer RF. The heater L4b is configured to be able to adjust the temperature of the reforming catalyst according to the temperature of the exhaust gas E flowing inside. Furthermore, downstream of the heater L4b, the exhaust gas flow path L4 is provided with a three-way catalyst CT1 that purifies the harmful components contained in the exhaust gas E, such as carbon monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NOx), and an SCR catalyst CT2 that removes nitrogen oxides (NOx) contained in the exhaust gas E. In this way, when a three-way catalyst CT1 is provided and the purpose is to mainly remove nitrogen oxides contained in the exhaust gas E using the three-way catalyst CT1, it is preferable that the control device R causes the engine body 40 to burn at stoichiometric ratio, in other words, causes the mixture of fuel and combustion air to burn at stoichiometric ratio in the combustion chamber (not shown) of the engine body 40.

[0034] In addition, an exhaust gas branch passage L4a is connected to the exhaust gas flow passage L4 between the engine main body 40 and the heater L4b, and this branch passage L4a branches off a portion of the exhaust gas E and allows it to flow. A three-way valve V2 is provided at the connection between the exhaust gas flow passage L4 and the exhaust gas branch passage L4a to adjust the distribution ratio between the flow rate of the exhaust gas E flowing through the exhaust gas flow passage L4 and the flow rate of the exhaust gas E flowing through the exhaust gas branch passage L4a. Furthermore, the exhaust gas branch path L4a is provided with a heat exchange section HE that exchanges heat between the exhaust gas E flowing through the exhaust gas branch path L4a and an external fluid (not shown), and is configured so that the exhaust heat of the exhaust gas E can be supplied to an external heat utilization section by the external fluid. That is, the engine system 100 of the present invention is configured as a cogeneration facility 200 that can supply shaft power from the engine body 40 and can also supply thermal power.

[0035] Incidentally, a rotation speed sensor that measures the rotation speed of the rotating shaft (not shown) is provided as the operating state detection unit 41 on the rotating shaft (not shown) of the engine body 40. Furthermore, a torque measurement sensor that measures the torque of the rotating shaft (not shown) of the engine main body 40 is provided as an operating state detection unit 41 on the rotating shaft of the engine body 40, and the control device R controls the opening of the engine injector IJ2, reforming injector IJ1, reforming throttle valve 12, main throttle valve 22, flow control valve V1, etc. so that the engine shaft output calculated based on the engine speed measured by the speed sensor and the torque measured by the torque measurement sensor becomes the target shaft output.

[0036] As explained above, the engine system 100 uses flame-retardant ammonia N as the main fuel and reformed gas K containing hydrogen as a combustion-promoting gas obtained by reforming a portion of the ammonia N as the auxiliary fuel to drive the engine body 40. From the viewpoint of improving the overall efficiency of the engine system 100, the engine system 100 according to this embodiment is configured as follows. That is, the engine system 100 is equipped with a heater L4b (an example of a temperature adjustment unit) that adjusts the temperature of the reformer RF using exhaust gas E from a combustion chamber (not shown), and the control device R is capable of performing ignition timing control that retards the ignition timing when performing output increase control that increases the shaft output, and advances the ignition timing when performing output reduction control that reduces the shaft output. Since ammonia N is flame-retardant, when the control device R executes the above-described ignition timing control, it is preferable to retard the ignition timing within a range from the first retard limit to a second retard limit on the top dead center side when natural gas is used as the fuel gas.

[0037] Furthermore, in the above-mentioned ignition timing control, the control device R is configured to be able to execute a retardation limit setting control in which the second retardation limit is set to the retard side as the hydrogen concentration of the reformed gas K measured by the hydrogen sensor S1 becomes higher, taking into consideration the stability of combustion in the engine body 40.

[0038] In addition, the control device R is configured to be able to execute retard amount correction control in the above-mentioned ignition timing control, in which the lower the hydrogen concentration of the reformed gas K measured by the hydrogen sensor S1, the smaller the amount of retardation of the ignition timing.

[0039] [Operation control by engine system] An example of control using the engine system 100 will now be described. In the engine system 100, when the control device R starts operation and the engine is operating at a predetermined output, if the output is to be increased, the control device R increases the output by executing retardation control (a concept included in ignition timing control) to retard the ignition timing (#01). That is, in step #01, retardation control (an example of ignition timing control) is used to retard the ignition timing, slowing the combustion in the combustion chamber and raising the temperature of the exhaust gas E. The exhaust gas E, now at a higher temperature, is then guided to the reformer RF, increasing the reforming rate (reforming efficiency) of ammonia N in the reformer RF, and the increased amount of reformed gas K (hydrogen) is then guided to the engine body 40, increasing the shaft output of the engine body 40. Furthermore, when the control device R starts operation and is operating at a predetermined output, if the control device R reduces the output, it reduces the output by executing advance control (a concept included in ignition timing control) that advances the ignition timing.

[0040] Furthermore, in the above-mentioned ignition timing control, the control device R measures the hydrogen concentration of the reformed gas K using the hydrogen sensor S1 (#02), and executes retardation limit setting control based on the measured hydrogen concentration. Specifically, the control device R sets the second retardation limit to the retard side (#03) because the higher the measured hydrogen concentration of the reformed gas K, the more likely it is that misfires in the combustion chamber will be suppressed due to the high ignition ability of the hydrogen contained in the reformed gas K. On the other hand, the lower the measured hydrogen concentration, the more the control device R sets the second retardation limit to the advance side.

[0041] In addition, in the above-mentioned ignition timing control, the control device R executes retard amount correction control based on the hydrogen concentration of the reformed gas K measured by the hydrogen sensor S1 (#04). Specifically, the lower the measured hydrogen concentration of the reformed gas K, the more the control device R executes retard amount correction control to correct the ignition timing retard amount to the smaller side. As a result, for example, when the ignition timing is retarded to increase the shaft output by a predetermined increment, and the reformer RF has not yet been sufficiently heated by the exhaust gas E and the hydrogen concentration of the reformed gas K from the reformer RF is low, the control device R corrects the retard amount to the smaller side, thereby preventing combustion from becoming unstable.

[0042] [Another embodiment] (1) In the above embodiment, the fuel flow passage L3 is configured to pass only ammonia N. However, the fuel flow passage L3 may be configured to pass ammonia N that has previously contained a highly combustible (ignitable) fuel such as hydrogen.

[0043] (2) In the above embodiment, a configuration example was shown in which the heater L4b that heats the reformer RF using the exhaust heat of the exhaust gas E was provided as the temperature adjustment unit that adjusts the temperature of the reformer RF. From the viewpoint of raising the temperature of the reformer RF before the exhaust gas E is discharged from the engine body 40, a configuration may be provided in which, for example, an electric heater (not shown) is provided in addition to the heater L4b.

[0044] (3) In the above embodiment, a configuration example was shown in which the heater L4b that heats the reformer RF using the exhaust heat of the exhaust gas E was provided as the temperature adjustment unit that adjusts the temperature of the reformer RF. Although the heater L4b is shown as being provided inside the housing (not shown) of the reformer RF in the example configuration, it may also be configured to heat the reforming air A1 flowing through the reforming air flow path L1.

[0045] (4) In the above embodiment, the engine system 100 is configured to perform stoichiometric combustion. However, in a configuration in which the SCR catalyst CT2 removes nitrogen oxides, lean combustion or rich combustion may be performed.

[0046] (5) In the engine system 100 according to the above embodiment, a control example in which the retard limit setting control and the retard amount correction control are executed has been shown. However, neither of these controls may be executed, or only one of them may be executed.

[0047] (6) In the above embodiment, a configuration example was shown in which the retardation amount correction control was executed based on the hydrogen concentration of the reformed gas K measured by the hydrogen sensor S1. As another configuration, as shown in Figure 3, a temperature sensor S2 (an example of a temperature measurement unit) is provided to measure a temperature-related value related to the temperature of the reformed gas K, and in the ignition timing control, the control device R may perform retard amount correction control in which the retard amount of the ignition timing is corrected to a smaller amount as the temperature-related value of the reformed gas K measured by the temperature sensor S2 becomes lower. Incidentally, the temperature-related value measured by the temperature sensor S2 may be the temperature of the reformed gas K at the outlet of the reformer RF, or may be the temperature inside the reformer RF.

[0048] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0049] The engine system of the present invention and the cogeneration facility equipped with the engine system can be effectively used as an engine system and a cogeneration facility equipped with the engine system, which can improve shaft output (improve thermal efficiency) through simple control while sufficiently reducing the energy supply related to the reforming of ammonia when ammonia and hydrogen obtained by reforming a part of the ammonia are used as fuel gas. [Explanation of symbols]

[0050] 40: Engine body 100: Engine system 200: Cogeneration facility A: Combustion air, reforming air CT1: Three-way catalyst E: Exhaust gas K: Reformed gas L4b: Heater L5: Reformed gas flow path L5a:Inflow part N: Ammonia R: Control device RF: Reformer S1: Hydrogen sensor S2: Temperature sensor

Claims

1. a control device for controlling the operation; a reformer that reforms a portion of the ammonia to generate a reformed gas containing a combustion-promoting gas having a high combustion rate, An engine system in which ammonia and the reformed gas generated in the reformer are combusted as fuel together with combustion air in a combustion chamber, a temperature adjusting unit that adjusts the temperature of the reformer using exhaust gas from the combustion chamber; The control device performs ignition timing control by retarding the ignition timing when performing output increase control to increase the axial output, and by advancing the ignition timing when performing output reduction control to reduce the axial output.

2. 2. The engine system according to claim 1, wherein the ignition timing control retards the ignition timing within a range from a first retard limit to a second retard limit located closer to top dead center when natural gas is used as the fuel gas.

3. a hydrogen concentration measuring unit for measuring the hydrogen concentration of the reformed gas; 3. The engine system according to claim 2, wherein the control device executes a retard limit setting control in the ignition timing control such that the second retard limit is set to a more retarded side as the hydrogen concentration of the reformed gas measured by the hydrogen concentration measuring unit increases.

4. a hydrogen concentration measuring unit for measuring the hydrogen concentration of the reformed gas; 3. The engine system according to claim 1, wherein the control device executes a retard amount correction control in the ignition timing control, in which the retard amount of the ignition timing is corrected to a smaller amount as the hydrogen concentration of the reformed gas measured by the hydrogen concentration measuring unit becomes lower.

5. a temperature measurement unit for measuring a temperature-related value related to the temperature of the reformed gas; 3. The engine system according to claim 1, wherein the control device executes a retard amount correction control in the ignition timing control, in which the retard amount of the ignition timing is corrected to a smaller amount as the temperature-related value of the reformed gas measured by the temperature measurement unit becomes lower.

6. The control device causes a mixture of the fuel and the combustion air to be stoichiometrically combusted in the combustion chamber, and 3. The engine system according to claim 1, further comprising a three-way catalyst in an exhaust passage through which exhaust gas from the combustion chamber flows.

7. A cogeneration facility comprising the engine system according to claim 1 or 2.

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